I mostly use cash. I hate getting the credit card bill after I get home - all the fun is over and now you have an unpleasant credit card bill.
And before someone says it.... yes.... traveling with a wad of cash has it's risks.

I bring hundreds and fifties as well as maybe a couple hundred in twenties. I don't expect to use the 100 dollar bills where I would get more than twenty dollars back in change, i.e., I'm only using the hundreds when the transaction calls for one. The fifties are not a problem but I'll still only use them when I get at most 20 bucks back in change. I have never had any problem with any vendor not taking the "larger" bills.